In my posts Eternal Youth, Overpopulation, And Instincts To Reproduce and Selective Pressure Grows For Belief In God I argued that a continued decline in fertility rates in industrialized countries seems unlikely because selective pressures are increasing the frequency of alleles that favor the desire to have offspring. Not everyone was persuaded by this argument, as the comments on those posts attest. Well, a new study by the CDC reports not only did fertility in the United States not decline in 2005, it actually increased slightly.
The number of births and the general fertility rate (GFR) increased slightly, whereas the crude birth rate remained unchanged from 2004 to 2005. The preliminary estimate of births in 2005, 4,140,419, increased 1 percent from 2004 (Tables 1, 5, 6, and 8) (2). Births rose for Hispanic, American Indian or Alaska Native (AIAN), Asian or Pacific Islander (API), and non-Hispanic black women, but declined slightly for non-Hispanic white women. The crude birth rate in 2005 was 14.0 births per 1,000 total population, unchanged from 2004. The preliminary 2005 GFR (66.7 births per 1,000 women age 15-44 years), however, rose slightly from 2004, to the highest level since 1993 (2). The GFR rose for Hispanic and AIAN women, declined slightly for API women, and was essentially unchanged for non-Hispanic white and non-Hispanic black women.
We are going to witness an increase in fertility as both genes and beliefs that favor fertility get selected for. It is not reasonable to expect the human race will escape selective pressures for higher fertility.
Even the development of biotechnologies for offspring genetic engineering will not stop natural selection from operating on the human genome. Natural selection operates on genetic variations. Whether the genetic variations are generated by chance events that generate mutations or by human minds choosing alleles from a catalog the result will be variations in offspring desire to have children of their own. Therefore selective pressures will still be able to work when we reach the point where people can make choices on which genes to give to their offspring.
It seems reasonable to expect that people who like children the most will be the ones who are most inclined to select genetic variations that cause their offspring to share their ardour for babies and children. Those children will have more children and will be more likely to give their children the same sorts of genetic variations. So how does reproductive biotechnology end natural selection? I do not see it happening unless governments intervene.
|Share |||Randall Parker, 2006 November 21 09:31 PM Trends Demographic|